An intelligent transportation system (ITS) provides vehicle operators with a wealth of information that enables the operators to make informed decisions about how they operate their vehicles. Information provided by an ITS may for instance notify an operator about the occurrence of an event that is pertinent to travel conditions in the area of his or her vehicle, such as the occurrence of traffic, an accident, hazardous road conditions, or the like.
In order for an ITS to provide this information to vehicle operators, vehicles are equipped with sensors and other information sources that detect the occurrence of these events. The information sources may detect, for instance, a low speed indicative of heavy traffic, an impact characteristic of an accident, or the skidding of a vehicle's tires on a slippery surface. An ITS application client associated with the detecting vehicle then generates an event notification message and transmits that message to surrounding vehicles via short-range wireless communications (e.g., dedicated short-range communications in the 5.9 Ghz band). Vehicles that receive the event notification message propagate the message to other vehicles, as appropriate, so as to form a vehicular ad-hoc wireless communication network (VANET).
This VANET, however, limits the ITS in some respects. As the population of ITS-enabled vehicles increases, the spectrum used for the VANET will become congested. The congestion will delay event notification message propagation and will therefore threaten the effectiveness of the ITS to provide event notification in a timely fashion. Furthermore, because the VANET relies on vehicle presence for message propagation, the VANET often only propagates event notifications to vehicles within the immediate area of an event.
These VANET limitations have prompted so-called cooperative ITSs (C-ITSs) that employ both a VANET and an infrastructure-based wireless communication network in a cooperative fashion. An infrastructure-based network in this regard includes for instance a cellular communication network (e.g., a Long Term Evolution, LTE, network, a High Speed Packet Access, HSPA, network, etc.) or any similar network that employs infrastructure for routing communications between communication endpoints. In such a C-ITS, the ITS application client associated with a vehicle transmits an event notification message to surrounding vehicles via the VANET, but also transmits the message to an ITS application server via the infrastructure-based network. The ITS application server determines the geographical area over which the event notification message is relevant (e.g., outside of the immediate vicinity of the event), and then sends the message to a so-called geomessaging server that distributes the message over the determined area via the infrastructure-based network.
Problematically, though, vehicles will not receive the event notification message from the ITS application server, even if they would have been able to receive the message via a VANET had they been near the event, if they are not configured to communicate with that server. A vehicle may not be configured to communicate with the ITS application server if the vehicle is not connected to the infrastructure-based network, e.g., because either the vehicle is not equipped with an interface capable of connecting to that network or the vehicle operator declines to pay for a subscription to the network. Or, even if the vehicle is connected to an infrastructure-based network, the vehicle may still not be able to communicate with the ITS application server if that network does not implement a geomessaging server.